H291 is a designation used in various contexts, often referring to a specific code or identifier. In the realm of aviation, it may relate to a particular flight route or aircraft model. In other fields, it could represent a product code or a classification within a system. In the context of health and safety, H291 might refer to a specific hazard classification, indicating a particular risk associated with a substance or material. Understanding such codes is essential for compliance and safety measures in industries like manufacturing and transportation.